The T-line (0.9351eV) luminescence center was created by radiation damage and/or annealing, at temperatures ranging from 400 to 600C, and was shown to contain one C atom and one H atom. Uniaxial stress and magnetic field measurements were reported here which showed that the center had monoclinic I symmetry, and created a deep electron level at Ec - 0.2eV. The formation mechanism and symmetry of the defect suggested that the center was an interstitial C atom plus a H atom.

A.N.Safonov, E.C.Lightowlers, G.Davies: Materials Science Forum, 1995, 196-201, 909-14